WO2001035488A1

WO2001035488A1 - Antenna arrangement

Info

Publication number: WO2001035488A1
Application number: PCT/SE2000/002220
Authority: WO
Inventors: Jari Paananen; Tony BJÖRKMAN
Original assignee: Avantego Ab
Priority date: 1999-11-10
Filing date: 2000-11-10
Publication date: 2001-05-17
Also published as: AU1428601A

Abstract

The present invention relates to an antenna arrangement (10), comprising a first antenna element (12), formed as a whip antenna, and a second antenna element (14), said first antenna element (12) being arranged to assume at least a first and a second operative position, and at one of said operative positions electrically coupling to said second and/or a third antenna element for constituting an antenna for a certain frequency band. The antenna arrangement further comprises at least one coupling means (17) arranged along a longitudinal axis of said second element (14), which coupling means is arranged to disconnect said second element in one of said operative positions, and that said first and second elements are connected in parallel when said coupling means connects said first and second antenna elements.

Description

TITLE

ANTENNA ARRANGEMENT

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an antenna arrangement, and specially a single, dual and/or multiband antenna arrangement, comprising a first antenna element, formed as a whip antenna, and a second antenna element, said first antenna element being arranged to assume at least a first and a second operative position, and at one of said operative positions electrically coupling to said second and/or a third antenna element for constituting an antenna for a certain frequency band.

BACKGROUND OF THE INVENTION

The wireless forms of communications have become a standard way of communication. There are many types of means for conducting a wireless communication, such as cordless telephones, lap top computers with wireless modems, satellite and cellular telephones. The communication device, i.e. the mobile handsets rapidly become smaller and lighter and the globalisation demand, multiple communication functions and standards being combined into a single unit, e.g. for communicates in multiple frequency bands. There are a variety of different radiotelephone systems in use today. These include different analogue or digital CDMA (Code Division Multiple Access) and TDMA (Time Division Multiple Access) based systems like GSM (Global System for Mobile telecommunication), AMPS (Advanced Mobile Phone System), DAMPS (Digital Advanced Mobile Phone System), PCS (Personal Communication Services), DCS (Digital Communication System), PCN (Personal Communication Networks), PDC 800 and 1500 and different cordless telephone systems.

Different systems operate in different frequency bands, thus requiring different antennas for maximum efficiency. The Swedish pending patent application No. 9902856-5, describes an antenna arrangement, comprising a first antenna element, in form of a whip, a second antenna element, in from of a coil or helical element, third antenna element, arranged as a socket and connection means. The first antenna element is arranged to assume at least a first and a second operative position, i.e. retracted or extracted. The first antenna element at one of said operative positions capacitively connects to said third antenna element constituting an antenna for a certain frequency band.

In this solution, however, the whip is capacitively connected to the helical element in pulled out position, which is not desirable in all applications. The problem is that, e.g. the helical antenna element is connected in parallel to the whip, which can disturb the function of the whip and the communication device

In US 5,926,140, an antenna for a portable radio unit includes a helical element, a rod-like whip element, a helical element power supply terminal, a whip element power supply terminal, a ground conductor, and a ground connection terminal. The helical element is arranged on a portable radio unit housing, and its diameter, pitch, and length are set in accordance with a carrier frequency having a wavelength lambda. The whip element is extended and stored by reciprocating inside a helical portion of the helical element, and is completely stored in the portable radio unit housing. The whip element has a length of lambda 12. The helical element power supply terminal is connected to one end of the helical element to supply power only to it when the whip element is stored. The whip element power supply terminal is arranged at a predetermined position of the helical element to supply power to the whip element through the helical power supply terminal and the helical element when the whip element is extended. The ground conductor is arranged on a lower end portion of the whip element through an insulating portion. The ground connection terminal grounds the ground conductor when the whip element is extended.

US5969684 describes a capacitive coupled extendable antenna for portable radio communication devices with improved operating characteristics. The extendable antenna includes a quarter-wavelength helical antenna, a quarter-wavelength whip antenna movable between the extended position and the retracted position through the helical antenna, and an electrically conductive sleeve acting as the feed point of the antenna. The helical antenna is electrically insulated from the sleeve so that the helical antenna is capacitively coupled to the sleeve. The whip antenna is enclosed within an insulating tube, which is disposed within a guide for longitudinal movement therethrough. The whip antenna is disposed in electrically insulated relation to the sleeve in the retracted position and electrically connected to the sleeve in the extended position via a stopper. When the whip antenna is in the extended position, the whip antenna is operative through direct coupling with the sleeve and when the whip antenna is in the retracted position, the helical antenna is operative through capacitive coupling with the sleeve. In a preferred embodiment, the whip antenna is short-circuited at the point of 90 DEG in electrical phase so as to form a lambda I balun. The resulting extendable antenna offers wider operating bandwidth and improved radiation efficiency when operating in the retracted or stand-by mode.

The invention according to EP 0747 989 relates to a double-action, two-piece antenna structure whose first antenna part, preferably a helix antenna, is fixedly connected to the antenna port of a radio communications set, and the second antenna port, preferably a rod antenna, is movable with respect to the said first antenna part. In an active position, the said second antenna part is coupled to the said first antenna part, forming a serial connection whose electrical length is as great as or greater than the electrical length of the first antenna part alone.

EP0825672 discloses an antenna structure, for two frequency ranges, there are two antenna elements, of which the first is a cylindrical coil conductor forming a helical antenna. It comprises, in the direction of its longitudinal axis, a first portion and a second portion, and the second antenna element is connected to the cylindrical coil conductor by a fixed connection at a junction lying between the first and second portions. The second antenna element may for example be a conductive filament, a conductive pattern formed on the surface of an insulating plate or a small-diameter helical antenna. The first operating frequency is dependent upon the combined electrical length of the portions of the first antenna element and the second operating frequency is dependent upon the combined electrical length of the lower part of the first antenna element and the second antenna element. The bandwidth of the operating frequencies is dependent upon the positioning of the junction in the first antenna element. In none of these documents an antenna arrangement, according to the invention are disclosed, which in one operative position disconnects a helical, meander shaped or type of antenna.

SUMMARY OF THE INVENTION

The main object of the present invention is to overcome the drawbacks of the prior art by means of a simple but yet an efficient antenna, which is easy to manufacture and assemble.

Another object of the invention is to provide an antenna enhancement wherein some of the above drawbacks of parallel coupling are eliminated.

Another object with the present invention is to provide means for impedance matching between different antenna elements of an antenna arrangement.

Therefore, the initially mentioned antenna arrangement further at least one coupling means arranged along a longitudinal axis of said second element, which coupling means is arranged to disconnect said second element in one of said operative positions. Said first and second elements are connected in parallel when said coupling means connects said first and second antenna elements.

Preferably, said second antenna element is a helical or meander antenna element and said coupling means is a washer.

In a preferred embodiment said second antenna element comprises of a first and a second end and that said coupling means is arranged at one end of said second antenna element.

The first element and said coupling means are coupled through one of galvanic, capacitive or inductive connections. The second element and said coupling means are coupled tlirough one of galvanic, capacitive or inductive connections. In one embodiment, in one of said operative positions the coupling means is arranged to function as an impedance matching arrangement.

Preferably, the antenna an antenna for high frequency bands in one of said operative positions.

The invention also refers to an antenna arrangement in a communication device, comprising et least a whip antenna element and a helical antenna element and antenna connection means for connecting said antenna arrangement to said communication device. The whip antenna element is arranged to assume at least a first and a second operative position, which at one of said operative positions, connects to said helical antenna element or a straight antenna element for providing an antenna for a certain frequency band. The antenna arrangement further comprises at least one coupling means arranged along a longitudinal axis of said helical element, which coupling means is arranged to disconnect said helical element in one of said operative positions. Preferably, straight antenna element is a substantially cylindrical socket. The whip antenna element is arranged coaxially to said helical element and said connector means. Most preferably, helical antenna element and said straight antenna element constitute a dual band antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be further described in a non-limiting way under reference to the accompanying drawings in which:

Fig. 1 is a schematic elevation view of an antenna arrangement according to the present invention,

Fig. 2 is a cross-section along the line II-II showing some part of the antenna according to fig.

1, Fig. 3 is a schematic view of a second embodiment of an arrangement according to the invention, Fig. 4 is a schematic view of a third embodiment of an arrangement according to the invention, and Fig. 5 is a schematic equivalent circuit diagram of the antenna arrangement according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

The preferred embodiment of the antenna arrangement 10, shown in figs. 1, 2 and 5, consists of three essentially main parts: an antenna housing 11, housing an antenna element 14, a whip component 12 and a connector part 13. The whip component 12 is shown in extracted position. The antenna is intended for on a communication unit, such as a mobile or cellular telephone handset (not shown).

The whip 12 comprises a substantially flexible conductor 121 coated with a protective and insulating layer 122, such as rubber or plastic. The whip 12 has a first end which can be provided with an end socket (not shown) of a conducting material and a second end having a stop boss 124, both ends of the whip may be provided with reinforcements 125 of a thicker plastic layer.

The housing 11 , preferably made of an insulating material, is hollow and comprises a first open end and a second end having an opening for the whip antenna 12, through which the whip can be retraced/extracted.

Inside the housing is arranged a second antenna element 14, formed as a coil constituting a helical antenna having a first free end 141 and a second end 142 connected (galvanically) to a conducting socket 15. The second end 142 of the helical antenna 14 has partially narrow pitches and connected to the conducting socket 15, e.g. through press fitting, screwing or the like.

The connector part 13 comprises a substantially cylindrical carrier 131 (or a carrier with another shape) of an insulating material (or conducting depending on the connection to the communications unit) having a first end 132 wedged inside a corresponding compartment in the housing 11 and a second end 133 provided with snap connection 134 in form of a hook, which is arranged to cooperate with a corresponding receiver in the communication unit (not shown) to attach the antenna arrangement to the same.

The connector member 136 has a first end in contact with the conducting socket 15 and a second end arranged for making contact with the receiver/transmitter parts of the communications unit and thus galvanically connecting the conducting socket 15 and the helical antenna element to 14 to the receiver/transmitter parts of the communications unit. However, the galvanic connection may be substituted with capacitive or inductive connections.

Between the whip 12 and the socket 15, a sleeve 16 of a dielectric or plastic material is arranged, which at its one end is fixed to the socket 15.

According to the invention a substantially ring-shaped washer 17 is arranged at the first open end of the housing 11. The washer 17 is, in this case, substantially L-shaped having a substantially horizontal section 171 and a substantially vertical section 172. The washer is fixed inside the housing through insertion of the edges of the substantially horizontal section 171 inside grooves 1 10 inside the housing 11. The substantially vertical section 172 is arranged to extend a substantially short distance inside the helical element 14 at its open end 141 , while the whip is arranged to extend through a hole in the centre section of the vertical section. The washer is made of a conductive material.

The function of the washer is to disconnect the helical element electrically in frequencies, which the antenna is arranged to operate when the whip is extended. The helical element 14 is connected to the washer galvanically, inductively or capacitively (galvanically in this case). The washer is in turn connected to the whip through galvanic, inductive or capacitive connection (capacitive in this case). Accordingly, when the whip is retracted it is not operative and only the helical antenna 14 and the socket 15 are operative as antennas, and the helical antenna blocks the high frequencies and functions as an antenna for a low frequency band. When the whip is pulled out the helical antenna 14 is short-circuited. In the retracted position the washer can be arranged so that it does not effect the helical element 14 (due to galvanic coupling) or so that it functions as an impedance matching arrangement. The whip is connected to the socket 15 through capacitive (or other) connection. Using the teachings of the invention, it is also possible to galvanically connect the whip to the socket 15.

In the illustrated embodiment, the whip is arranged substantially coaxially in the centre of the helical antenna. The whip is so arranged that there is no galvanic connection between it and the rest of the antenna, neither at the retracted position nor at the pulled out position. When the whip is pulled out, preferably in its entire length so that the end socket 123 is placed inside the socket 15, it makes a capacitive contact with the socket 15, preferably using the sleeve 16 as the dielectric member of the capacitor. Moreover, the sleeve functions as a fixing element, which sustains the whip at pulled out position (or retracted position in corporation with the reinforcement 125 at the other end of the whip) when the end socket bears on the sleeve.

It is of course possible to arrange the whip parallel to the helical element and arrange the connector (washer) in suitable location for disconnecting the helical element. Also the helical element can be substituted or cooperate with a meander element.

In one embodiment as shown in fig. 3 the washer 370 can be integrated on the whip 320, e.g. as a bump, which at a certain position electrically couples to the helical element and disconnects the helical element 340 as described above.

In another embodiment as shown in fig. 4, the helical/meander element 440 can be arranged with geometrical variation(s) 470 which electrically disconnects it at a desired position(s) in cooperation with the whip 420, i.e. the same disconnection effect obtained through the above- mentioned washer.

It is also possible to integrated the washer 370 on the whip 320, e.g. as a bump, which at a certain position electrically disconnects the helical element 340 as described above.

The overall function of the antenna arrangement is as follows. The helical antenna 14 and the socket 15 constitute the dual band antenna, thereby constituting resonators for two different frequency bands. The helical antenna acts as a blocking element whereby the helical antenna 14 and socket 15 compose the low frequency band antenna and the socket 15 the high frequency band antenna. The whip 12 is used for enhancement of the antenna characteristics, and therefore it is important that a balanced capacitive connection is obtained to achieve good performance for all desired frequencies.

The characteristics of the capacitive connection can be changed by changing the lengths of the end socket of the whip, socket 15 or sleeve 16 or the material it is made of. It is also possible to form antenna elements with different electrical length by arranging several conducting sleeves in different positions along the length of the whip. Moreover, the helical antenna can be substituted with any other antenna elements such as an additional whip, a meander antenna etc.

Furthermore, the sleeve 16 can be arranged displaceable on the end socket; or both: the end socket 123 and the sleeve 16 can be arranged fixed inside the socket 15 and the end of the whip can be arranged to contact the socket.

In dual or multi band applications the washer can be placed in a suitable position along the helical elements extension length. It is also possible to arrange two or more washers.

Clearly, other coupling means such as breakers, (micro) switches or similar can be arranged to connect or disconnect the antenna elements. Moreover, the shape of the washer can be varied and adapted to the antenna appearance.

The antenna arrangement according to the invention can be used in any device with a need for receiving and/or transmitting electro-magnetic waves, and because of its small size it is most suitable for use in cellular phones or the like.

The invention is not limited to the shown embodiment but can be varied in a number of ways, e.g. through combination of two or more embodiments shown, without departing from the scope of the appended claims and the arrangement and the method can be implemented in various ways depending on application, functional units, needs and requirements etc. REFERENCE SIGNS

10 Antenna

11 Housing

12 Whip 320, 420

121 Conductor

122 Protective layer

124 Boss

125 Reinforcement

13 Connection means

131 Carrier

132 First end

133 Second end

134 Snap connection

14 Helical antenna 340, 440

141 First end

142 Second end

15 Socket

16 Sleeve

17 Washer/Coupler 370, 470

171 horizontal section

172 Vertical section

Claims

1. An antenna arrangement (10), comprising a first antenna element (12), formed as a whip antenna, and a second antenna element (14), said first antenna element (12) being arranged to assume at least a first and a second operative position, and at one of said operative positions electrically coupling to said second and/or a third antenna element for constituting an antenna for a certain frequency band, characterised in the antenna arrangement further comprises at least one coupling means (17) arranged along a longitudinal axis of said second element (14), which coupling means is arranged to disconnect said second element in one of said operative positions, and that said first and second elements are connected in parallel when said coupling means connects said first and second antenna elements.

2. The antenna arrangement of claim 1, characterised in, that said second antenna element (14) is a helical or meander antenna element.

3. The antenna arrangement according to any of preceding claims, characterised in, that said coupling means (17) is a washer.

4. The antenna arrangement according to any of preceding claims, characterised in, that said second antenna element (14) has a first and a second end (141; 142) and that said coupling means (17) is arranged at one said first or second ends.

5. The antenna arrangement according to any of preceding claims, characterised in, that in one of said operative positions the coupling means is arranged to function as an impedance matching arrangement.

6. The antenna arrangement according to any of preceding claims, characterised in, that it is an antenna for high frequency bands in one of said operative positions.

7. The antenna arrangement according to any of preceding claims, characterised in, that said first element (12) and said coupling means (17) are coupled through one of galvanic, capacitive or inductive coupling.

8. The antenna arrangement according to any of preceding claims, characterised in, that said second element (14) and said coupling means (17) are coupled through one of galvanic, capacitive or inductive coupling.

9. The antenna arrangement according to claim 1, characterised in, that said coupling means is integrated on said first element.

10. The antem a arrangement according to claim 1 , characterised in, that said coupling means is a geometry variation of said second element.

11. An antenna arrangement (10) in a communication device, comprising et least a whip antenna element (12) and a helical antenna element (14) and antenna connection means (13) for coupling said antenna arrangement to said communication device, said whip antenna element (12) being arranged to assume at least a first and a second operative position, which at one of said operative positions couples to said helical antenna element (14) or a straight antenna element (15) for providing an antenna for a certain frequency band, characterised in that the antenna arrangement further comprises at least one coupling means (17) arranged along a longitudinal axis of said helical element (14), which coupling means is arranged to disconnect said helical element in one of said operative positions.

12. The antenna arrangement according to claim 11, characterised in, that said straight antenna element is a substantially cylindrical socket (15).

13. The antenna arrangement according to claim 12, characterised in, that said whip antenna element is arranged coaxially to said helical element and said coupling means.

14. The antenna arrangement according to any one of claims 11 -13, characterised in, that said helical antenna element and said straight antenna element constitute a dual band antenna.